<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>

</body>
<script>

// console.log('123' == 123);       //true
// console.log('' == null);         //false
// console.log('' == 0);            //true
// console.log([] == 0);            //true
// console.log([] == '');           //true
// console.log([] == ![]);          //true
// console.log(null == undefined);  //true
// console.log(Number(null));       //0
// console.log(Number(''));         //0
// console.log({} + 10);            //[object Object]10
// console.log(parselnt(''));       //不知道报错没去查也
    let obj = {
        [Symbol.toPrimitive]() {
            return 200;
        },
        valueOf() {
            return 300;
        },
        toString() {
            return 'hello'
        }
    }
    console.log(obj + 200);
</script>

</html>